The invention relates generally to the art of polyurethanes for use in laminated transparencies, and more particularly to the art of thermoplastic polyurethanes for use as interlayers.
Safety glass is a well known term for a glass sandwich composed of an interlayer bonding together two glass plates or sheets so that breaking the glass results in minimum dispersion of broken glass fragments. These laminated glasses are widely used in automobiles, and the interlayer must possess a number of properties, among which are: (1) high impact energy absorption to minimize concussive injury; (2) shear and tear strength sufficient to prevent rupture of the interlayer by the broken glass; (3) sufficient adhesion to the glass to inhibit laceration on contact with and prevent dispersion of broken glass and (4) good optical quality. Moreover, safety glass laminates must possess these properties over a wide temperature range in which these materials are employed.
It has been discovered that bilayer and multiple-layer laminates of one or more sheets of glass and particular urethane polymers can be employed to provide safety glass which is impact-resistant over a wide temperature range, minimizes lacerative injury and is superior to safety glass using polyvinyl butyral interlayers.
U.S. Pat. No. 3,764,457 to Chang et al discloses safety glass laminates comprising a thermoplastic polyurethane sheet prepared from an aliphatic polycarbonate, a cycloaliphatic diisocyanate and a monomeric aliphatic diol.
U.S. Pat. No. 3,931,113 to Seeger et al discloses polyester urethanes for use in safety glass laminates which are formed from a cycloaliphatic diisocyanate, a low molecular weight diol, and a hydroxy-terminated polyester of polycaprolactone, poly(butyleneladipate), poly(butylenelazelate) or mixtures thereof.
U.S. Pat. No. 4,131,605 to Ammons discloses a transparent elastomeric polyurethane which may be cast and cured in place at ambient temperature prepared by the reaction of a cycloaliphatic diisocyanate with a polyalkylene ether glycol and a crosslinking agent in the presence of butyl stannoic acid catalyst.
U.S. Pat. No. 4,131,606 to Ammons discloses a transparent elastomeric polyurethane which may be cast and cured in place at ambient or slightly elevated temperatures prepared from a homogeneous colorless liquid reaction mixture of a polycaprolactone polyol, a cycloaliphatic diisocyanate and butyl stannoic acid catalyst.
U.S. Pat. No. 4,241,140 to Ammons discloses a transparent elastomeric polyurethane useful as an interlayer in safety glass laminates prepared by the reaction of an aromatic diisocyanate with a mixture of a polyalkylene ether glycol, a polycaprolactone triol and a monomeric aliphatic diol.
While the above described polyurethane interlayers are effective energy-absorbing, impact-resistant materials for laminating glass to glass, a thermoplastic interlayer which facilitates lamination of rigid plies with different coefficients of thermal expansion is needed for laminating materials such as polycarbonate or acrylic and glass for use in aircraft windshields and other transparencies.